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close with no comment again ! I don't know how can he/she do that :))
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hqtMay 27 '12 at 17:01

The difference is subtle, because we tend to infer a lot from the phrase "manage the backlog".

While a PM is often responsible for coordinating HOW the initiative should be accomplished, the Product Owner is responsible for understanding WHAT the product show do and works with the team to make sure this is reflected in the list of items (often described in business terms as features) called the Product Backlog.

In Scrum, the Development Team (composed of all skills needed to produce a complete increment in an iteration) is responsible for determining HOW to accomplish the items selected for completion in an iteration.

I think you ask this because you don't understand so much about agile.

Project Manager : he decides EVERYTHING, and tester, developers... often don't talk together, they must talk with project manager, and project manager will give this idea to other. for example : developer says : "I have add this feature A". and project manager will says to tester : "Hey, you should add a unit test for feature A", for example.

Product Owner : yeah, Project Manager can be a Product Owner, or, your customer can be product owner, too. It means : Product Owner : the person who can control the flow how the software is !
More over, product owner : he just looks how you work and give some talk to control the FLOW, not control your activity.